Selectively permeable materials are useful in a broad range of applications, including for example, chemical and/or biological protective clothing, separation membranes, fuel cell membranes, medical equipment, such as filters and masks, as well as medical apparel. Of particular concern in providing materials adapted to these uses is the selectivity profile necessary to function as intended. For example, a material provided as protective clothing must not only inhibit passage of toxins through the protective membrane from the external environment to the internal side, the material must also allow the passage of water vapor from the internal side to the external environment. Since the absence of adequate transpiration of water causes discomfort at the least and dangerous overheating if prolonged, water vapor passage characteristics are of paramount importance in designing materials for use in applications such as those listed above.
Materials and articles of manufacture designed to be selectively permeable include those detailed in U.S. Pat. Nos. 5,468,574; 5,679,482; 5,840,387; 6,110,616; 6,395,383; 6,187,696; 5,824,405; 5,743,775; 5,740,551; 5,391,426; 5,273,814; 5,260,360; 5,024,594; 4,943,475; 4,515,761; 4,510,193; 4,469,744; 4,194,041; and 4,039,440.
However, there is still a need for a lightweight, low cost material that combines the characteristics of flexibility over a broad temperature range, high transport of air and water vapor and low transport of harmful chemicals.